The present invention relates to an ultrasonic joining method and an ultrasonic joining device for bonding paper materials, in particular paper, paperboard or cardboard.
In the European patent Application EP 0 340 334 A2, a device is described which is suited for bonding two- or multilayered paper products by means of ultrasonic sound. The paper used is thereby provided with a thermoplastic coating. The longitudinal waves are generated by means of the ultrasonic horn, so that said ultrasonic horn is moved towards the anvil and moved again away from the anvil when ultrasonic vibrations occur. A sufficient compression of the paper layers is generated by the corresponding ultrasonic frequency and the corresponding contact pressure. At the same time, a high degree of heat development occurs in the micro-range of the thermoplastic coating and therefore for the adhesive bonding of the paper layers.
The attached FIG. 6 shows an ultrasonic joining device 100 according to the prior art for bonding thermoplastically coated paper material in a schematically simplified view. The device 100 comprises an ultrasonic horn 102 according to the prior art and an anvil 103 according to the prior art. The paper material 5 to be joined is located between the ultrasonic horn 102 and the anvil 103. A joining pressure 106 is applied to the paper material 5 in the gap between ultrasonic horn 102 and anvil 103. The ultrasonic horn 102 generates an ultrasonic vibration having a vibration direction 107. The vibration direction 107 and the direction of the joining force 106 are aligned parallel to one another in the device 100 according to the prior art. The longitudinal movement direction of the ultrasonic horn 102 is thus used for the joining process.